silent killer,

Cardiovascular System Overview

  • Delivered by Mrs. Krista K. Fowler, MSN, RN, NP-C
    Email: ksklemm@ua.edu

Functions of the Cardiovascular System

  • Vital functions include:

    • Delivers vital oxygen and nutrients to cells

    • Removes waste products from the body

    • Transports fluids, electrolytes, and hormones

  • Arteries: Carry blood away from the heart

    • Composed of three layers:

    • Tunica intima: Inner layer made of endothelial cells; metabolically active and in contact with blood.

    • Tunica media: Middle layer of smooth muscle and nerve fibers.

      • Constriction (alpha-adrenergic stimulation)

      • Dilation (beta-adrenergic inhibition)

    • Tunica adventitia: Outer layer of supportive connective tissue.

    • Key for regulating blood flow under high volume and pressure.

  • Veins: Carry blood back to the heart

    • Composed of three layers similar to arteries.

    • More compliant than arteries.

    • Utilize valves and muscle contraction to promote venous return.

  • Capillaries: Site of exchange between blood and tissues.

Arterial Disorders

  • Arterial Structure:

    • Blood carried away from the heart via the aorta with three distinct wall layers.

  • Arterial Endothelium:

    • Acts as a semipermeable barrier between the vessel and tissue.

    • Injury leads to endothelial dysfunction which can result in:

    • Atherosclerosis

    • Coronary artery disease

    • Diabetes mellitus

    • Hypertension

    • Hypercholesterolemia

    • Smoking effects.

Cardiac Output (CO)

  • CO represents the volume of blood expelled from the left ventricle per minute.

  • It is considered a gold standard measure for the heart's effectiveness as a pump.

  • A normal CO value is approximately 5 L/min.

  • Determinants of CO:

    • Stroke volume (SV): Volume of blood expelled with each left ventricular contraction, averaging around 70 mL/contraction.

    • Ejection fraction: Percentage of diastolic volume ejected during systole.

    • Heart rate (HR): Number of times the left ventricle contracts in a minute.

    • Formula: CO=HR×SVCO = HR \times SV

Factors Influencing Cardiac Output

  • Preload: Volume of blood in the left ventricle prior to contraction.

  • Afterload: Resistance the left ventricle must overcome to eject blood.

  • Contractility: The force of left ventricular contraction.

Blood Pressure (BP)

  • Defined as the force blood exerts on vessel walls.

  • BP is represented as a fraction:

    • Systolic: Measures cardiac contraction (normal <120 mmHg)

    • Diastolic: Measures cardiac relaxation (normal <80 mmHg)

    • Example: 132/82 mmHg indicated a systolic BP of 132 mmHg and diastolic BP of 82 mmHg.

    • Pulse pressure is around 40 mmHg, calculated as the difference between systolic and diastolic (SBP - DBP).

  • Peripheral Vascular Resistance (PVR): Resistance to blood flow in vessels.

  • Blood Pressure equation: BP=CO×PVRBP = CO \times PVR

Mean Arterial Pressure (MAP)

  • Major indicator of cerebral perfusion; desired MAP > 60 mmHg.

  • Calculation formulas:

    • MAP=13SBP+23DBPMAP = \frac{1}{3} SBP + \frac{2}{3} DBP

    • OR MAP=(SBP+2×DBP)3MAP = \frac{(SBP + 2 \times DBP)}{3}

Blood Pressure Regulation

Nervous System Regulators

  • Parasympathetic Nervous System (PNS)

    • Affects the heart via the vagus nerve leading to decreased heart rate but has no direct effect on vessels.

  • Sympathetic Nervous System (SNS)

    • Impacts both heart and vessels via spinal cord:

    • Causes vasoconstriction (alpha receptors) and increases heart rate and contractility.

Receptor Regulators

  • Baroreceptors: Sensitive to blood pressure changes; located in arteries and stimulate SNS response upon pressure drops.

  • Chemoreceptors: Monitor changes in blood chemistry affecting BP regulation.

Hormonal Regulators

  • RAAS System: Activates when BP or blood volume decreases, triggering renal reabsorption of water/sodium and potassium excretion.

  • Vasopressin (ADH): Causes vasoconstriction and reabsorption of water in kidneys.

  • ANP and BNP: Hormones released when BP or blood volume increases; promote natriuresis (excretion of water and sodium).

Hypertension

  • Defined as a prolonged elevation in blood pressure.

  • Major risk factors include excessive cardiac workload due to increased afterload and vasoconstriction.

Types

  • Primary Hypertension:

    • Most common form (90-95% of cases).

    • Develops gradually with no known cause.

  • Secondary Hypertension:

    • More sudden and severe; resulting from pathology in other systems/organs.

    • Both forms are significantly risk-laden for coronary artery disease (CAD), stroke, and myocardial infarction (MI).

Risk Factors

  • Advancing age, ethnicity (higher prevalence in African Americans), family history, obesity, diabetes, sedentary lifestyle, tobacco use, high sodium/low potassium/Vitamin D diet, excessive alcohol consumption, and stress.

Diagnosis

  • Involves medical history, physical examinations, multiple blood pressure readings across different times, with a waiting period of 5 minutes between assessments.

  • Laboratory tests also help determine organ damage presence.

Manifestations

  • Often termed the